<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>todolist</title>
    <style type="text/css">
        .list_con {
            width: 600px;
            margin: 50px auto 0;
        }

        .inputtxt {
            width: 550px;
            height: 30px;
            border: 1px solid #ccc;
            padding: 0px;
            text-indent: 10px;
        }

        .inputbtn {
            width: 40px;
            height: 32px;
            padding: 0px;
            border: 1px solid #ccc;
        }

        .list {
            margin: 0;
            padding: 0;
            list-style: none;
            margin-top: 20px;
        }

        .list li {
            height: 40px;
            line-height: 40px;
            border-bottom: 1px solid #ccc;
        }

        .list li span {
            float: left;
        }

        .list li a {
            float: right;
            text-decoration: none;
            margin: 0 10px;
        }
    </style>
    <script type="text/javascript" src="./js/jquery-1.12.4.min.js"></script>
    <script>
        $(function () {
            var $button = $('#btn1');
            var $txt = $('#txt1');
            var $ul = $('#list');

            $button.click(function () {

                if ($txt.val() === "") {
                    return;
                }

                var $addLi = $('<li><span>' + $txt.val() + '</span>' +
                    '<a href="javascript:;" class="up"> ↑ </a><a href="javascript:;" class="down"> ↓ </a>' +
                    '<a href="javascript:;"\n class="del">删除</a></li>');

                $ul.append($addLi);

                $txt.val('');

            })

            $ul.delegate('a', 'click', function () {
                var Str = $(this).prop('class');
                if (Str === 'del') {
                    $(this).parent().remove();
                }
                else if (Str === 'up') {
                    if (!$(this).parent().prev().length) {
                        alert('到顶了');
                        return;
                    }
                    $(this).parent().prev().before($(this).parent());
                }
                else{

                    if (!$(this).parent().next().length) {
                        alert('到底了');
                        return;
                    }

                    $(this).parent().next().after($(this).parent());
                }
            })
        })
    </script>

</head>

<body>

<div class="list_con">
    <h2>To do list</h2>
    <input type="text" name="" id="txt1" class="inputtxt">
    <input type="button" name="" value="增加" id="btn1" class="inputbtn">

    <ul id="list" class="list">

        <li><span>学习html</span><a href="javascript:;" class="up"> ↑ </a><a href="javascript:;" class="down"> ↓ </a><a
                    href="javascript:;"
                    class="del">删除</a></li>
        <li><span>学习css</span><a href="javascript:;" class="up"> ↑ </a><a href="javascript:;" class="down"> ↓ </a><a
                    href="javascript:;"
                    class="del">删除</a></li>
        <li><span>学习javascript</span><a href="javascript:;" class="up"> ↑ </a><a href="javascript:;" class="down">
                ↓ </a><a href="javascript:;"
                         class="del">删除</a></li>

    </ul>

</div>
</body>

</html>